1. Field of the Invention
The present invention relates to a deburring apparatus, and, more particularly, to a deburring apparatus capable of automatically removing burrs formed on the surface of, for example, upset steel pipes for oil wells.
2. Description of the Related Art
Since oil drilling takes place under coarse conditions, the steel drilling pipes require excellent strength in the main pipe sections thereof as well as in the threaded coupling portions for joining the steel pipe sections.
The strength of the above-described threaded joining portion may become insufficient since the thickness of the pipe wall is inevitably reduced. Therefore, if more strength is necessary, the thickness of the wall of the end portion of a pipe which is threaded to make it suitable for joining is increased by upset forging work before conducting the thread forming work.
Upset forging is, as shown in FIGS. 14(A) and 14(B), a kind of machining for increasing the thickness of the wall of the end portion of a steel pipe 1 by forcibly inserting a punch 3 in the direction designated by an arrow into the end portion of the steel pipe 1 which is positioned between an upper half mold 2A and a lower half mold 2B.
However, the molds 2A and 2B for use in the upset forging are so chamfered at the joints thereof as shown in FIG. 14(C) as to protect the outer surface of the steel pipe 1 from being bitten by the joints of the mold due to plastic deformation during the forging.
Therefore, burrs 1A and 1B are formed in two places in the circumferential direction of the steel pipe 1 as shown in FIGS. 15(A) and 15(B) during the upset forging, the burrs 1A and 1B being formed in the direction along the axis of the steel pipe 1.
That is, burrs are inevitably formed on the outer surface of the upset pipes or cast products at the position corresponding to the portions at which the joints of the half upset molds or casting dies are coupled to each other. Since such burrs deteriorate the quality of the machinings and products from the ensuing processes, they must be removed by hand work with, for example, a rotary whetstone. Since deburring work with a rotary whetstone requires heavy manual labor and the problem of dust arises, it is preferable that such burrs be removed without direct human labor.
(1) However, in the case where the deburring work with the rotary whetstone is simply automated, a complicated or irregularly changed shape of the material to be machined or nonuniform shape of the burrs will cause the material to be bitten by the whetstone or cause failure to remove all the burrs.
An object of the present invention is to provide a deburring robot capable of reliably removing burrs formed on the surface of the workpiece even when the surface has a complicated or an irregularly changed shape or when the shape of the burrs are nonuniform.
(2) When the deburring work with a rotary whetstone is intended to be automated, it might be considered of providing a copying claw capable of copying the surface of the workpiece and of positioning the whetstone with a specified positional relationship kept with the copying nail. This leads to the fact that the whetstone can be so relatively moved as to trace the surface of the workpiece by virtue of the action of the copying nail. As a result, the burrs can be thoroughly removed without a fear of biting the workpieces.
However, with the structure in which a copying nail of the type described above is used, a whetstone is worn in accordance with the time elapsed, causing its positional relationship with the copying nail to be inevitably changed. Therefore, even if the copying nail reliably, performs its roll of copying the surface of the workpiece, a perfect deburring effect by the whetstone cannot be expected.
Another object of the present invention is to improve accuracy in the deburring effect by suitably modifying the positional relationship between the copying nail and the whetstone when the whetstone is worn.
(3) In the case where the deburring work with a rotary whetstone is intended to be automated, a multiplicity of whetstones must be frequently used when the whetstone is completely worn or in order to correspond to variations in workpieces. Therefore, it is necessary to reliably and readily renew the worn whetstone with no fear of deterioration in the operation rate.
A further object of the present invention is to readily renew the whetstone with no fear of deterioration in the operation rate.
(4) If the burrs are not removed after the upset forging, the following problems arise:
1 In the case where the upset forging work contains a multiplicity of manufacturing processes to satisfy the designed increase ratio of the thickness of the workpiece, burrs formed in the first process bite the forged portion in the next process, causing a problem of quality to arise.
2 The retained burrs deteriorate the accuracy of the threads and the life of the cutter during the threading process.
3 The interference of the burrs with the coupling forconnecting steel pipes prevents a suitable clamping.
4 The burrs deteriorate the appearance and therefore the quarity of the product.
Therefore, in order to remove the burrs, an apparatus capable of removing the burrs is necessary. However, the unmanned deburring work causes the following problems:
1 Since there are variations in the sizes of the pipes and in the upset shapes, the automated deburring apparatus must quickly and reliably correspond to the variable workpieces in order to reliably detect the positions of the burrs and remove the burrs.
2 The deburring apparatus must reliably correspond to variations in the upset shapes whith are due to the changes in the size of the pipe. For example, the upset length is varied by changes in the wall thickness of the pipe as shown in FIG. 16.
3 The deburring apparatus must also reliably correspond to variations in the shapes of the burrs which are due to changes in the size of pipe. For example, if the upset length is changed due to a change in the wall thickness of the pipe, the upsetting force becomes nonuniform as shown in FIG. 17. This leads to the fact that the dimensions of the gap formed in the aperture in the mold change, causing the shape of the burrs to the vary.
A still further object of the present invention is to reliably detect the positions of the burrs and to remove the thus detected burrs even if the upset shape or the shape of the burrs are varied due to changes in the size of the pipe, the reliably detecting the positions of the burrs and reliably removing the same corresponding to variations in sizes of the pipes and upset shapes.